Disclosed is a personal watercraft capable of obtaining a high horsepower in a high engine speed even when a four-cycle engine is mounted in the personal watercraft limited in length. The personal watercraft adapted to eject water from an outlet port to be propelled as the resulting reaction, comprises: a multi-cylinder four-cycle engine contained in an engine room and having even cylinders of four or more cylinders; a water jet pump being driven by the engine, for pressuring and accelerating the water; primary collecting exhaust passages, each of which is configured to collect two exhaust passages respectively connected to exhaust ports of two cylinders of the engine into one exhaust passage; and a secondary collecting exhaust passage configured to collect the primary collecting passages.
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7. A small boat propelled by a multi-cylinder four-cycle engine disposed in an engine room of the boat, comprising:
a plurality of exhaust passages respectively connected at front end portions to exhaust ports of the engine; at least two collecting exhaust passages, the collecting exhaust passages being connected to rear ends of the exhaust passages, the collecting exhaust passages being integral with each other and defined by a separating plate; and an inlet port configured to introduce water to an inside of the collecting exhaust passages, the inlet port being provided at a rear end portion of each of the exhaust passages or a front end portion of each of the collecting exhaust passages.
10. A personal watercraft adapted to eject water from an outlet port to be propelled as a resulting reaction, comprising:
a multi-cylinder four-cycle engine contained in an engine room and having even cylinders of four or more cylinders; a water jet pump being driven by the engine, for pressuring and accelerating the water; exhaust passages respectively connected at front end portions to exhaust ports of the cylinders; primary collecting exhaust passages connected to rear end portions of the exhaust passages, the primary collecting exhaust passages being configured to collect two of the exhaust passages into one exhaust passage; and a secondary collecting exhaust passage into which the primary collecting exhaust passages are merged, wherein the rear end portion of each of the primary collecting exhaust passages is configured to protrude into an inside of the secondary collecting exhaust passage.
3. A personal watercraft adapted to eject water from an outlet port to be propelled as a resulting reaction, comprising:
a four-cycle engine contained in an engine room and having four cylinders; a water jet pump being driven by the engine, for pressurizing and accelerating the water; exhaust passages respectively connected to exhaust ports of the cylinders; primary collecting exhaust passages each of which is configured to collect two exhaust passages into one exhaust passage; and a secondary collecting exhaust passage configured to collect the primary collecting exhaust passages, wherein each exhaust passage is an exhaust manifold through which an exhaust gas from the exhaust port of each cylinder flows to the primary collecting exhaust passage, wherein each primary collecting exhaust passage is comprised of a primary collecting exhaust pipe, and wherein the secondary collecting exhaust passage is a muffler comprising at least one expansion chamber.
1. A personal watercraft adapted to eject water from an outlet port to be propelled as a resulting reaction, comprising:
a multi-cylinder four-cycle engine contained in an engine room and having even cylinders of four or more cylinders; a water jet pump being driven by the engine, for pressuring and accelerating the water; exhaust passages respectively connected at front end portions to exhaust ports of the cylinder; primary collecting exhaust passages connected to rear end portions of the exhaust passages, the primary collecting exhaust passages being each configured to collect two of the exhaust passages into one exhaust passage; a secondary collecting exhaust passage into which the primary collecting exhaust passages are merged; and an inlet port configured to introduce water to an inside of the primary collecting exhaust passages, the inlet port being provided at a rear end portion of each of the exhaust passages or a front end portion of each of the primary collecting exhaust passages.
2. The personal watercraft according to
4. The personal watercraft according to
5. The personal watercraft according to
6. The personal watercraft according to
8. The small boat according to
9. The small boat according to
11. The personal watercraft according to
an inlet port configured to introduce water to an inside of the primary collecting exhaust passages, the inlet port being provided at a rear end portion of each of the exhaust passages or a front end portion of each of the primary collecting exhaust passages.
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1. Field of the Invention
The present invention relates to a personal watercraft (PWC) which ejects water rearward and planes on a water surface as the resulting reaction. More particularly, the present invention relates to a personal watercraft having a characteristic exhaust system.
2. Description of the Related Art
In recent years, so-called jet-propulsion personal watercraft have been widely used in leisure, sport, rescue activities, and the like. The jet-propulsion personal watercraft is configured to have a water jet pump that pressurizes and accelerates water sucked from a water intake generally provided on a bottom of a hull and ejects it rearward from an outlet port. Thereby, the personal watercraft is propelled.
In the jet-propulsion personal watercraft, a steering nozzle provided behind the outlet port of the water jet pump is swung either to the right or to the left, to change the ejection direction of the water to the right or to the left, thereby turning the watercraft to the right or to the left.
In the personal watercraft, an engine is contained in an engine room located substantially at the center portion of the watercraft in the longitudinal direction and surrounded by a deck and a hull. As the engine, a two-cycle internal combustion engine (two-cycle engine) that is small and lightweight and is capable of generating a high power is employed. Recently, the use of a four-cycle internal combustion engine (four-cycle engine) has been contemplated.
When the four-cycle engine is accommodated in the engine room for the two-cycle engine and is required to have a horsepower as high as that of the two-cycle engine, a horsepower per displacement of the engine needs to be increased in the four-cycle engine.
In the four-cycle engine, it is necessary to extend an exhaust passage in order to obtain the high horsepower. Nevertheless, since the personal watercraft is short in total length and the engine is mounted at the center portion of the watercraft, it is hard to extend the exhaust passage to such an extent that the high horsepower can be obtained in the four-cycle engine.
The present invention addresses the above-described problem, and an object of the present invention is to provide a personal watercraft capable of obtaining a high horsepower when a four-cycle engine is mounted in the personal watercraft limited in total length.
According to a first aspect of the present invention, there is provided a personal watercraft adapted to eject water from an outlet port and to be propelled as the resulting reaction, comprising: a multi-cylinder four-cycle engine contained in an engine room of the watercraft and having even cylinders of four or more cylinders; a water jet pump being driven by the engine, for pressuring and accelerating the water; exhaust passages respectively connected to exhaust ports of the engine; primary collecting exhaust passages each of which is configured to collect two exhaust passages into one passage; and a secondary collecting exhaust passage configured to collect the primary collecting exhaust passages.
In the personal watercraft so constituted, all the exhaust passages can be efficiently collected in the relatively small engine room in such a manner that two exhaust passages are collected into the primary collecting exhaust passage, and then, the primary collecting exhaust passages are collected into the secondary collecting exhaust passage. With such a structure, by utilizing exhaust inertia, exhaust efficiency is increased regardless of the limited length of an exhaust path. In addition, the exhaust system can be simply and efficiently structured. The secondary collecting exhaust passage may be a collecting exhaust passage obtained by extending the primary collecting exhaust passage into one passage, or otherwise a muffler.
Preferably, two exhaust passages connected to cylinders ignited at successive timings may be collected into one primary collecting exhaust passage.
Preferably, an inlet port may be provided at a rear end portion of the exhaust passage or a front end portion of the primary collecting exhaust passage, for introducing water to an inside of the primary collecting exhaust passage. This makes it possible that the temperature of the exhaust gas flowing through the inside of the primary collecting exhaust passage can be lowered. As a result, the actual primary collecting exhaust passage achieves an effect normally provided by a longer primary collecting exhaust passage. This structure is advantageous to the personal watercraft that is short in total length and is configured to have an engine mounted substantially at the center portion of the watercraft.
Preferably, the secondary collecting exhaust passage may be configured to accommodate at least an extended rear end portion of the primary collecting exhaust passage.
In the structure, since the two exhaust passages of the engine are collected into each primary collecting exhaust passage, and at least a rear end portion of the primary collecting exhaust passage is extended to be accommodated in the secondary collecting exhaust passage, the primary collecting exhaust passage can be extended even in the engine room that is limited in space. This structure is advantageous to the personal watercraft that is short in total length and is configured to have the engine mounted substantially at the center portion of the watercraft.
Preferably, the engine may be a four-cylinder engine, the exhaust passage may be an exhaust manifold through which an exhaust gas from the exhaust port of each cylinder flows to the primary collecting exhaust passage, the primary collecting exhaust passage may be comprised of a primary collecting exhaust pipe, and the secondary collecting exhaust passage may be a muffler comprising at least one expansion chamber.
Preferably, two primary collecting exhaust pipes may have semi-circular cross-sections which are joined to have a circular cross-section. This structure is suitable for the relatively small engine room. Further, a penetrating hole through which the joined primary collecting exhaust pipe is introduced into the muffler is a circular hole which is easy to process. Further, when a water jacket of a double-pipe shape is provided at the outer periphery of the primary collecting exhaust pipe to attain a water-cooling structure, an outer casing of the water jacket that is cylindrical and easy to process can be attained.
Preferably, the two primary collecting exhaust pipes may constitute one pipe having two independent passages defined by a separating plate having a curvature in cross-section. The separating plate can absorb thermal distortion caused by thermal change by changing the curvature.
Preferably, the muffler may be a water muffler in which the exhaust gas containing supplied cooling water flows. This offers higher muffling effect in the personal watercraft.
According to a second aspect of the present invention, there is provided a small boat propelled by a multi-cylinder four-cycle engine disposed in an engine room of the boat, comprising: a plurality of exhaust passages respectively connected to exhaust ports of the engine; at least two collecting exhaust passages, each of which is configured to collect the plurality of exhaust passages, the collecting exhaust passages being integral with each other and defined by a separating plate; and an inlet port provided at a rear end portion of the exhaust passage or at a front end portion of the collecting passage, for introducing water to an inside of the collecting exhaust passage.
In accordance with the small boat so constituted, when the primary collecting exhaust passage is comprised of one pipe having two independent passages defined by the separating plate, the exhaust gas and the separating plate which is subjected to increased thermal load are cooled by the water introduced through the inlet port, so that thermal load is reduced. As a matter of course, the present invention is applicable to personal watercrafts which are one type of the small boat.
Preferably, the inlet port may be provided to allow water to be supplied to the separating plate through the inlet port. Thereby, since the separating plate is positively cooled, the heat load acting on the separating plate can be further reduced.
Preferably, the separating plate may be provided so as to form an angle with respect to a horizontal line in a steady state of the small boat. This makes it possible for water to be supplied to the separating plate through the inlet port regardless of the direction in which the inlet port is opened. More preferably, the separating plate is provided vertically.
The above and further objects and features of the invention will be more fully be apparent from the following detailed description with accompanying drawings.
Hereinafter, a personal watercraft, which is one type of a small boat according to an embodiment of the present invention, will be described with reference to the accompanying drawings.
Referring now to
As shown in
An engine E is disposed in an engine room 20 surrounded by the hull H and the deck D below the seat S.
In this embodiment, the engine E is a four-cycle engine having multiple (for example, four) cylinders comprised of even cylinders. As shown in
In
As shown in
In
In the personal watercraft according to this embodiment, the engine having an exhaust system in
The engine E is ignited in the order of a first cylinder to which the exhaust pipe 1A is connected, a third cylinder to which the exhaust pipe 1C is connected, a second cylinder to which the exhaust pipe 1B is connected, and a fourth cylinder to which the exhaust pipe 1D is connected. In brief, the engine E is ignited in the order of the first cylinder, the third cylinder, the second cylinder, and the fourth cylinder.
The exhaust pipe 1A of the first cylinder and the exhaust pipe 1D of the fourth cylinder which are ignited at successive timings are collected into a primary connecting exhaust pipe 2A placed downstream of the exhaust pipes 1A, 1D in an exhaust gas flow path. At least a rear end portion (for example, a rear half portion) of the primary connecting exhaust pipe 2A is accommodated in a water muffler 3 in which cooling water is supplied to the exhaust gas flowing through the inside. The exhaust pipe 1B of the second cylinder and the exhaust pipe 1C of the third cylinder which are ignited at successive timings are collected into a primary collecting exhaust pipe 2B placed downstream of the exhaust pipes 1B, 1C. At least rear end portion of the primary collecting exhaust pipe 2B is accommodated in the water muffler 3. In this embodiment, the water muffler 3 is a secondary collecting exhaust passage.
In this embodiment, as shown in
Since the primary exhaust pipes 2A, 2B are formed in the form of one pipe, only a circular hole is formed in an end plate 3A of the water muffler 3 for inserting the primary collecting exhaust pipes.
In
The water muffler 3 is comprised of a plurality of chambers (expansion chamber or the like) which are connected to one another by means of a communicating pipe 3d, thus constituting a labyrinth structure. A resonator 3R is provided at a rear end portion (left end portion in
In
Alternatively, as shown in
As shown in
Further, alternatively, as shown in
Still further, alternatively, as shown in
As shown in
In the personal watercraft constituted as described above, the following functions and effects can be obtained.
In the case where the engine E is placed substantially at the center portion of the watercraft in the longitudinal direction as shown in
Since the inlet ports 2a, 2b are provided at the front end portions of the primary collecting exhaust pipes 2A, 2B for introducing water to the inside of the pipes 2A, 2B to thereby effectively lower the temperature of the exhaust gas, the effect provided by using pipes longer than the actually used pipes is achieved. Further, the engine E is capable of increasing a power even in a low engine speed by utilizing exhaust pulsation, as in a high engine speed.
In the exhaust system of the present invention, the increased power can be obtained without extending the length from the tip end of the engine E to the rear end of the water muffler 3. Therefore, the four-cycle engine with high horsepower can be mounted without the necessity of extending the total length of the personal watercraft.
As described with reference to
While the four-cycle engine having four cylinders has been described in the above embodiment, the exhaust system of the present invention is applicable to any other four-cycle engine having even cylinders with pairs of cylinders.
While the muffler is the water muffler in the above embodiment, a muffler that does not introduce water may be employed.
While the four exhaust passages 1A-1D in
Numerous modifications and alternative embodiments of the invention will be apparent to those skilled in the art in view of the foregoing description. Accordingly, the description is to be construed as illustrative only, and is provided for the purpose of teaching those skilled in the art the best mode of carrying out the invention. The details of the structure and/or function may be varied substantially without departing from the spirit of the invention and all modifications which come within the scope of the appended claims are reserved.
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Oct 08 2002 | MATSUDA, YOSHIMOTO | Kawasaki Jukogyo Kabushiki Kaisha | ASSIGNMENT OF ASSIGNORS INTEREST SEE DOCUMENT FOR DETAILS | 013468 | /0348 |
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